1. Field of the Invention
This invention relates generally to filters and, more particularly to aquarium filter devices for use within saltwater and freshwater aquariums.
2. Description of the Prior Art
It is generally understood that to maintain the health and vitality of the animals confined to an aquarium, provision must be made for continuous filtration, aeration and recirculation of the aquarium water. It is further understood that three types of filtration processes are necessary to maintain optimum environmental conditions within the aquarium, namely: chemical filtration to remove dissolved organics; mechanical filtration to remove suspended matter; and biological filtration which utilizes beneficial bacteria to neutralize toxic substances within the aquarium water.
A number of differently configured aquarium filter systems have been devised in an attempt to meet these needs. One such system is the external aquarium filter in which a filter housing is located outside the aquarium tank, either beneath the tank floor or adjacent to the tank sidewall and depended from the upper edge thereof.
A typical external filter system consists of an electrically powered pump, intake and return lines, a filter housing containing activated charcoal overlaid with one or more layers of synthetic filter medium, and a means for aerating the aquarium water. As water is siphoned out of the aquarium tank via an inlet tube, it moves through the filter housing inlet chamber into the central housing chamber where it passes through the filter medium into the housing outlet chamber and is pumped back into the aquarium via the return line.
Although the external filter device is generally adequate for providing chemical and mechanical filtration, the filter material utilized in such a device is not sufficient to support the large colony of bacterial growth needed to achieve optimum biological filtration. Another problem with the external aquarium filter is that it clogs rapidly and must be frequently changed to maintain the quality and clarity of water within the aquarium.
Another type of aquarium filter system presently in use is the underwater aquarium filter, specifically designed for placement within the aquarium tank. This type of system is comprised of inlet and outlet tubes, a pumping device, a means for aerating the aquarium water, and a filter housing composed of inlet and outlet chambers and a central chamber for containment of a filter medium such as activated charcoal overlaid with one or more layers of synthetic filter media. Water from the aquarium is pumped through the inlet tube to the filter housing where it passes from the inlet chamber through the filter medium in the central chamber to the outlet chamber and exits the housing for return to the aquarium tank via the outlet tube.
One problem inherent in the underwater aquarium filter concerns its size. Since such a system is dimensionally configured so as to be unobtrusive when placed within the aquarium tank, its filter housing is relatively small. Therefore, the volume of filter material contained within the housing is generally not sufficient to provide adequate mechanical filtration nor can it support a large enough colony of desireable bacteria to provide effective biological filtration. Another problem with this type of system is that the filter medium clogs very quickly and must be frequently replaced. Further, because the filter is positioned underwater within the aquarium tank, the filter housing must be physically separated from the system and removed from the aquarium tank to accomplish replacement of the filter medium; a procedure which disturbs the aquarium environment and interrupts the entire filtering process.
A third type of aquarium filter is known as the undergravel filter. This type of system employs a perforated filter element positioned at the bottom of the aquarium tank. A layer of aquarium gravel is distributed across the top surface of the filter element to provide biological and mechanical filtration of the aquarium water. A pumping device and means for aerating the aquarium water are also provided. When the pumping device is activated, water from the upper region of the aquarium moves downward through the gravel and through the perforations in the filter element. After passing through the filter element to the bottom of the aquarium tank, water is drawn into a recirculation tube and discharged back into the upper region of the tank.
The efficiency of an undergravel filter device is dependent upon its ability to permit the water circulating through the aquarium tank to flow freely and evenly through the perforations in the device's filter element. However, since the filter element utilized in most currently patented undergravel filter systems is comprised of a thin section of synthetic material containing a number of spaced apart perforations, water flow through the element is restricted to the areas of perforation resulting in uneven water flow, impaired filtration, rapid growth of harmful algae and the accumulation of untreated wastes within the aquarium tank. Additionally, as untreated wastes accumulate in the gravel overlying the filter element, the gravel "packs" creating dead spots through which water cannot circulate. And, since harmful algae and solid waste materials also accumulate on the filter element, the entire system must be frequently removed from the aquarium for cleaning; a labor intensive process that necessitates the removal of all animals from the aquarium tank.
Another difficulty encountered with the use of currently available undergravel filter systems is the lengthy break-in time required to stabilize the pH of the aquarium water before animals may be safely placed within the aquarium tank; typically 5 to 6 weeks. In addition, each time the filter system is removed from the aquarium for cleaning, the colony of desireable bacteria contained in the gravel is destroyed making it necessary to repeat the break-in process before animals may be safely returned to the aquarium.
Another disadvantage noted in existing undergravel filter devices is that they are not suitable for use in specialized aquariums such as saltwater reef tanks and coral tanks, nor can they be easily and inexpensively manufactured to fit within spherical or other unusually configured aquarium tanks.